Copper base alloy



Feb. 21, 1939. 1M, KELLY 2,147,844

COPPER BASEy ALLOY Filed June 19, 1937 g A gez'ng 717776 i12 How's af 5006.

Patented `Feb. 2l, 1939 PATENT OFFICE oorrER BASE ALLOY James M. Kelly, Trafford, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation o! Penn- Sylvania Application June 19, 1937, Serial No. 149,146l

9 Claims.

This invention relates to alloys, and particularly to copper base alloys which have improved mechanical, thermal and electrical properties and the utilization of the alloys as articles of manufacture.

Certain metals have been alloyed with copper` to produce an alloy having better mechanical properties, but generally such alloys have been inferior to copper as conductors of electricity and 10 heat. In the copper base alloys which have been produced and which have the desired conductlvity or mechanical strength, the characteristics y teristics of high physical strength and high electrical and thermal conductivity when precipitation hardened.

A further object of this invention is to utilize a copper base alloy formed to shape, and precipitation hardened to give high physical strength and high electrical and thermal conductivity.

'A more specific object of this invention is to produce by the use of alloying elements having low solid solubility in copper, a copper base alloy which may be precipitation hardened to give it high physical strength and conductivity and will retain its strength' and resistance to creep when subjected to moderately elevated temperatures.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, in which:

Figure 1 is a graph illustrating the hardness values obtained for a representative alloy of this invention by subjecting it to a suitable heat treatment.

Fig. 2 is a graph illustrating the characteristics of hardness and conductivity given different representative alloys of this invention when subjected to the suitable heat treatment, and

Fig. 3 is a graph illustrating the results obtained as measured bythe product of hardness and conductivity for different ratios of the alloying elements in alloys containing different amounts of the alloying elements.

In order to produce a copper base alloy'which will have desired mechanical and electrical properties, metals which can be precipitated to effect a dispersion of ne particles throughout a copper base when suitably heat treated, are added 5 to the copper melt. It has been discovered that a copper base alloy containing even small proportions of cobalt and iron has excellentme chanical and electrical properties when suitably heat treated. 1c'

In preparing the alloy, the metals cobalt and iron may be added directly to the copper melt in any suitable form such as powders or lumps, since neither cobalt nor iron are easily oxidized as compared to copper. The alloying content may thus be maintained substantially constant during the hot forming operations, since the alloying elements will not be lost by oxidation at the surface of the alloy.

In practice, the alloy may be prepared by heating a melt of copper, such as commercial electrolytic copper, under a covering of charcoal in a graphite crucible and adding theV cobalt and iron in any suitable massive form to the copper melt. In order to permit complete deoxidation of the melt, the temperature of the melt of copper, cobalt and iron may be held at between 1150 C. and 1200 C. for a period of time suicient for the completion of the reaction of the graphite crucible with the oxygen. Where desired the alloy may also be prepared by heating the melt of copper and alloying elements in` a ceramic crucible with a cover of lump charcoal over the surface of the melt. Although not always necessary as in the making of other copper base al- 35 loys, where desired small quantities of calcium or phosphorus or other suitable deoxidizers may be added to the melt of copper, cobalt and iron to insure complete deoxidation of the melt. The metals cobalt and iron are readily soluble in copper and enter into solution, providing an alloy in which the alloying elements are uniformly distributed throughout the structure.

The alloy may be cast in massive, intricate or iine form in any suitable type of mold, such as a "sand casting or chill cast mold. Where desired, the alloy may be cast directly into the predetermined shape of the article which is to be manufactured, after which it may be easily machined as required or it may be cast to a pattern suitable for forging to the desired shape. In its cast condition the copper-cobalt-iron a1- loy is comparatively ductile, being easily forged or drawn to shape.y

Alloys comprising from small but eiiective amounts up to by weight of each of the alloying metals cobalt and iron with the balance substantially copper, when heat treated, as hereinafter described to precipitation harden them, have been found to have high physical strength and good electrical and thermal conductivities.

In order to develop the mechanical strength and the electrical properties of the alloy, it may be subjected to a precipitation hardening treatment comprising subjecting the allow to a high temperature below the melting point of the alloy for obtaining a high solid solution of the alloying metals in the copper, quenching the alloy from the high temperature to retain the alloying metals in the solid solution and then reheating the alloy to a lower or ageing temperature and holding it at this temperature for a period of time sufficient to precipitate the alloying elements from the solid solution state. In practice, heating at a temperature of between 750 C. and 1075 C. is found to effect a high solid solution of the alloying metals in the copper while a reheat at a temperature of between 450 C. and 600 C. effects an efiicient precipitation of the alloying constituents.

Alloys comprising copper, cobalt and iron within the ranges hereinbefore given when heat treated as described have a high Rockwell B hardness and good conductivity. The heat treatment described is found to be of special benefit to alloys comprising between .5% to 3% of each of the elements cobalt and iron with the balance substantially copper. As specific examples of the alloys thus prepared and heat treated and the results obtained, the following are tabulated. In the table, the copper content is omitted, it being understood that the balance of the alloying content comprises copper with possible incidental impurities occurring during the alloying process.

sisting of quenching from 1000 C. and ageing the alloys at 500 C. for different periods of time up to 100 hours are illustrated by the curves of the graph of Fig. 2 of the drawing. In this iigure, curves I5, I1 and I9 illustrate the conductivity values obtained by heat treating alloys numbered I3, I2 and I 0, respectively, while curves I6, I8 and 20 illustrate the Rockwell B hardness values obtained for alloys I3, I2 and I0, respectively. From these curves it will be noted that an increase in the conductivity values is obtained at a small sacrice of the hardness values. However, it will be noted that after ageing these alloys for a period of time of 35 hours at the temperature of 500 C., each of the alloys has a conductivity of 60% or greater while the hardness value approximates 80 Rockwell B.

Referring to Fig. 3 of the drawing, curves 22, 24 and 2B illustrate a peculiar relation between the cobalt and iron contents of the alloys of this invention. In this graph, the product of the Rockwell B hardness and the conductivity values obtained for different representative alloys is plotted against the ratio of the cobalt to the iron content of the alloys. Since the highest value of both hardness and conductivity is desired in the alloys of this invention, the product of hardness and conductivity when plotted against the ratio of the cobalt-iron content is illustrative of the results obtained, since a variation in the hardness or conductivity is possible without change in the value of theproduct by overageing. Such a variation is possible since an increase in conductivity y is obtained at a sacrifice of hardness. Curve 22 is representative of a combined cobalt and iron content ranging between .9% to 2%, curve 24 is representative of a combined cobalt and iron content ranging between 2.8 and 3.2% while curve 26 Conduc- Ageing Ratio Sum Hardness Product Alloy No. Fe Co %Co/%Fe %CO+%F8 B tivlty KXRB tgig; 1;!

l. 75 1. 04 0. 6 2. 79 81 65 5285 50 98 98 1. 0 1. 96 70 59 4130 100 2. 01 2. 07 1. 12 4. 08 80 60 4800 15 2. 01 2. 07 1. 12 4. 08 79 62 4898 45 2. 01 2. 07 1. 12 4. 0B 76 03 4788 100 3. 00 1. 77 59 4. 77 80 60 4800 35 3. 00 1. 77 59 4. 77 79 62 4888 100 92 95 l. 1 1. 87 70 59 4130 100 2. 95 95 32 3. 90 70 62. 5 4340 35 53 42 79 95 62 65 4030 35 l. 47 l. 48 99 3. 0 59 7l 4899 25 1. 98 .93 47 3.0 73 6l 53 25 The alloys identified in the above given table were subjected to a heat treatment consisting of quenching them from a temperature of 1000 C. and reheating or ageing them at a temperature of 500 C. for diierent periods of time, as indicated in the table. The ratio of the cobalt to the iron content of the alloy and the sumv of these alloying elements listed in the table are given for reasons as will be understood hereinafter.

Referring to the drawing and to Fig. 1 in particular, curves I0, II, I2 and I3 are illustrative of the hardness values imparted to alloy number I0 identified in the hereinbefore given table when subjected to different heat treatments consisting of quenching from temperatures of 850 C., 900 C., 950 C. and 1000 C., respectively, and then aged at a temperature of 500 C. It will be noted from these curves that as the quenching temperature approaches the melting point of the alloy, the hardness values obtained increases.

Some representative conductivity and hardness values obtained by subjecting different alloys within the range given to a heat treatment conis representative of a combined cobalt and iron content ranging between 3.9% and 4.8%.

From these curves it is evident that the best properties may be obtained in alloys whose cobalt to iron ratio is between .5'and 1.25 and whose composition of cobalt plus iron is between 3.9% and 4.8%. In each of the curves plotted for the diiferent cobalt plus iron contents, it is noted that there is a peak of maximum values of the product of conductivity and hardness at a ratio of the cobalt to iron content approximating 1. It is noted that for the higher ratios of cobalt to iron, the product of the conductivity and hardness values decreases at a fast rate for the alloys within each of the ranges of the cobalt plus iron content. It is thought that this is because the high cobalt content for the iron concentration of the alloys retards the hardening or precipitation phenomena. Another possible explanation is that there is a greater solubility of cobalt with the increasing ratio of cobalt to iron. From these curves it can generally be said that the best results may be obtained in the copper base alloys the manufacture of large castings, such as commutator segments. Other uses of the alloy are as Welding electrode tips or welding wheels or other articles where a conductivity of 60% or greater is required together with high physical strength. These alloys may also be efficiently employed in applications such as cylinder heads for internal combustion engines where high thermal conductivity is desired combined with high physical strength. The alloys may be cast directly into the predetermined shape of the article of manufacture or into a pattern suitable for forging or drawing.

It is, of course, to be understood that this invention is described with reference to a fspecic embodiment thereof and that other and various modifications may be made without in any way departing from the spirit of the invention as set forth in the appended claims.

I claim as my invention:

1. An alloy comprising copper, cobalt and iron, the cobalt ranging from a small but effective amount up to v% and the iron ranging from a small but effective amount up to 5% with the balance substantially all copper.

2. An alloy comprising from about .5% to 3% of cobalt, from about .5% to 3% of iron, with the balance substantially all copper.

3. An alloy comprising copper, cobalt and iron, the cobalt ranging from a small but effective amount up to 3% and the iron ranging from a small but eiective amount up to 3% with the balance substantially all copper, the ratio of the cobalt to the iron being between .5 and A1.25 to 1.

4. An alloy comprising from .9% to 3% of cobalt, from about .9% to 3% of iron with the balance substantially all copper, the combined cobalt and iron content ranging from about 3.9% to 4.8%.

5. An age hardened alloy comprising from about .5% to'3% of cobalt, from about .5% to 3% of iron with the balance substantially all copper which has been quenched from a temperature of between 750 C. and 1075 C. and aged at a temperature of between 450 C. and 600 C.

6. As an article of manufacture, an alloy comprising from .5% to 5% cobalt, from .5% to 5% iron with the balance substantially all copper, formed to a predetermined shape and precipitation hardened to give high physical strength and high conductivity.

7. A alloy comprising about 1.04% of cobalt, about 1.75% of iron and the balance substantially all copper.

8. 'An alloy comprising about 2.07% of cobalt, about 2.01% of iron and the balance substantially all copper.

9. An alloy comprising from about .9% to 3% of cobalt, from about .9% to 3% of iron with the balance substantially all copper, the combined cobalt and iron content ranging from about 3.9% to 4.8% with the ratio of the cobalt to the iron being between .5 and 1.25 to 1.

JAMES M. KELLY. 

